Automatic telephone system



y 9, 1931. H. M. FRIENDLY 1,806,288

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2' 1928 14 Sheets-Sheet 1 Inveniur- Herheri-P'I'Friendlg y 1931. H. M. FRIENDLY 1,806,288

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2'? 923 14 Sheets-Sheet 2 a Nilll Fig-2,

l nveninfl Herb EIfi-I TFriBndl y 1931. H. M. FRIENDLY 1,806,288

AUTOMA'II C TELEPHONE SYSTEM Filed Feb. 27 923 14 Sheets-Sheet 3 Inveniur- H erher'i-PfFr-ie ilg 7 May 19, 1931. H. M. FRIENDLY AUTOMAT I C TELEPHONE SYSTEM Filed Feb. 2'7 1923 14 Sheets-Sheet 4 Fig.4

Inv an ar- I-Ierh eri-P'I-F'rlejg May 1931. H. M. FRIENDLY 1,806,288

AUTOMATIC TELEPHONE SYSTEM Filed 1928 14 Sheets-Sheet 5 L'TWF'J Fig 51.

May 19, 1931. H. M. FRIENDLY 1,306,238

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2''! 1928 IA Sheets-Sheet 6 Inveniur Herb efl-P'I'F'r'rig y 1931. H. M. FRIENDLY 1,806,288

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 27 1928 14 Sheets-Sheet 7 AHg.

y 9, 1931. H. M. FRIENDLY 1,806,288

AUTOMAT I C TELEPHONE SYSTEM Filed Feb. 27 1928 14 Sheets-Sheet 8 Fig-5- Inveninr- Her-h eflP'I-Friendlg y 1931. H. M. FRIENDLY AUTOMATIC TELEPHONE SYSTEM Filed Feb. 27 1929 14 Sheets-Sheet 9 Inventor Herberi-Pl-Fr'iendlg AL I- mui 65% y 9, 1931. H. M. FRIENDLY 1,806,288

AUTOMAT IC TELEPHONE SYS TE! 14 Sheets-Sheet 10 Filed Feb. 27 192 FIL JEL Inventor Her]: wl-P'Hriendlg May 19, 1931.

H. M. FRIENDLY 1,306,283

AUTOMATI C TELEPHONE SYSTEM Filed Feb. 27 1923 14 Sheets-Sheet l l Fiqlly '9, 1931. H. M. FRIENDLY 1,806,288

AUTOMATI C TELEPHONE SYS TEL! Filed Feb. 1928 14 Sheets-Sheet l2 Inveninry 1931. H. M. FRIENDLY 1,806,288

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 27 923 14 Sheets-Sheet 15 Fig-14- FiqlB- Invaninr- Her]: afl-IiI-Friendly a W y 1931. H. M. FRIENDLY 1,806,288

AUTOMATIC TELEPHONE SYSTEM Filed Feb. 27 192B 14 Sheets-Sheet 14 Patented May 19, 1931 UNITED STATES PATENT OFFICE HERBERT M. FRIENDLY, OF CHICAGO, ILLINOIS; MILTON S. FRIENDLY AND CENTRAL TRUST GOM'PANY OF ILLINOIS EXEGUTOBS OF SAID HERBERT M. FRIENDLY, DE-

cnasiro AUTOMATIC TELEPHONE SYSTEM v Application filed Fetmary 27, 1928. Serial' No. 257,480. r

5 General objects The general objects of the present invention are to enable a subscriber of the automatic telephone-system, who contemplates temporarily leaving the location of his telephone, to directively set central office apparatus or eallforwarding equipment associated with his line through the agency of his automatic calling device dial on his telephone so that in case any calls are thereafter directed to his line, the latter said calls will be further extended or forwarded to a predetermined random subscribers line or other line of the system; The latter said line may terminate at the switchboard of an attendant operator who is charged with responding to such calls and imparting such information to the party calling as instructed by the absent subscriber primarily called. That is, for example, a physician before leaving his oflice may remove the receiver of. his telephone as if to initiate a call, and then operate his calling device dial by placing his forefinger in a s ecific depression finger-hold of the dial an then draw the dial until his finger encounters the finger-stop, so that whenlthe dial is released it willsend a series of eleven open impulses. After the dial has returned, he will restore the receiver, leaving his central office call-forwarding equipment in the set condition. The same kind of manual operation will un-set the said set condition. General operation Reference is made to my Patent No. 1,772,713, granted Aug. 12, 1980. Also, to my Patent No. 1,800,788 granted April 14, 1931. These pending applications are directed to a telephone s stem and apparatus having objects general y as set forth in the foregoing statements. However, the present invention is directed to a telephone system having features and objects not present in the disclosures in the foregoing references, while at the same time the said reference applications incorporate fea:

tures lookin to objects not disclosed in the present app ication. These latter features may be incorporated in the present disclosure.

In general, it may be stated that the present invention, as compared to the disclosures in said applications made of reference, looks to reducin the amount of equipment through. employing certain elements in common with a p urality' of lines arranged for forwarding callsin place of employing-equipment used solely for an individual line. There are a num er of other features of the present invention not present in the applications made of reference in-the fore-going. Among the said'other features are:

a. An impulse sending mechanism for directing the forwarding of calls which mechanism is common to a plurality of lines arranged so that calls made to a random one of said lines may be forwarded to a predetermined line or lines of the system, directed 'by the common impulse sending mechanism.

When a call is made to a line set for forwarding the call, arelay specific to said line is operated, to in turn cause a finder switch to initiate its operation and select and seize the line called and thereby extend the line called to a first selector, or selector of the lowest rank in the system. Incidental to selecting and seizing the called line, ap aratus is prepared for sending a train of 1m ulse series which is predetermined in accor ance with the line to which such calls are to be sent by pre-arrangement. The present disclosure shows two methods of accomplishing the sending of the proper train of series correspending to the line called primarilyby the wipers and finds the set line under call, one of the said wipers is then resting upon a bank terminal which corresponds to the winding of a relay specific to the line under call. Under the seized co dition of the finder switch this relay will be operatively energized so that its contacts will close circuit paths for settin up a stored condition in the impulse sen ing mechanism for sending a train of series which will operate the first selector and successive switches to forward the call from the line primarily called to the line which is to finally receive the call because of the set condition of the line primarily called.

The said first method, because of having an irn ulse sending mechanism individual to the nder switch, thus disables the impulse sending mechanism from further use until the finder switch becomes idle due to the termination of the call last forwarded. L

The second or preferred method, which will be described later on, contemplates a finder switch generally like the finder switch used in the said first method, but in place of havin an impulse sending mechanism individua to the finder switch, has a group of three impulse sending mechanisms (in the exemplary embodiment disclosed herein) common to a larger plurality of said finder switches. The latter said plurality may be fifty or more, depending upon the trafiic to i be handled.

Under the said referred method, when the call is progressed to a set called line, one

of the finder switches will hunt for and seize the said set called line. Responsive to the latter said seizure of the set called line a second finder switch individual to one of the said three impulse sending mechanisms will start its hunting operation to find and seize the finder switch which last 0 erated to seize the set line called. When this finder switch, or any other finder switch not yet ecu-operated with an impulse sending mechanism, is found and seized by the said second finderswitch, a relay individual to the set line called and corresponding to the relay used in the said first method, is operatively energized to set the impulse sending mechanism individual to the said second finder switch so that a train of impulse series is thereupon sent to forward the call to the predetermined line of the system which is to finally receive the call. The preferred method is essentially like the said first method, in so far as the impulse sending mechanism is concerned, since each said mechanism contains a relay specific to each line which may be primarily called by a calling party which also may be set for forwarding calls. However, a second finder switch is inter osed for co-operating a common said mechanism with a random one of a plurality of first finder switches arranged for co-operating with a set line called.

I). A connector J is shown having access to operator answering jacks. These jacks are on an attendant operators switchboard. The, operator will perceive calls to the respective jacks by the glowing of a companion lamp when a call is forwarded from a line primarily called which said line has been set so that the call will be forwarded to the jack on the attendants switchboard specific to it. That is to say, the connector J is reached by the impulse sending mechanism sending an impulse train constituting three digits 111. These three digits will be followed by a series constitutin two more digits to operate the connector to select the desired answering jack. The last two digit series thus identifies the line of a hundred-group which was i primarily called by the calling party. The attendant will be able to res ondwith a full knowled e of the line whic was primarily called. he may take any message for the wanted subscriber or give any instructed in-.

connection already exists to the jack through some other connector. Under the condition of the calling party receiving the busy tone he may await his turn, as he will be able to gain talking connection with the jack only n the corresponding time order in which the Jack was selected by a waiting connector.

\Vhenthe attendant withdrawslthe answer-r.

ing plug to terminate a conversation the jack will be seized from the next in order waiting connector. The said order of waiting is determined by the order of calling through the agency of order of access switches which constantly predetermine the order of access in accordance with the order of selecting the jack, automatically. The latter takes into account any calls which may be abandoned without upsetting the'relative order df access. Under the arrangement a single jack is provided specific for each subscriber to the attendants services regardless of the number of calls which may be held in abeyance each with its attained order of access, at the same time.

(1. Means are provided for apprising the attendant while she is in communication with a callin party if there is any other party (or parties) awaiting his turn tobe responded to by her, so that she may dispose of the party t en in communication as soon as possible in view of the party or parties awaiting their turn for a response from her through the same jack as then in use.

There are a number of other features of the present invention believed to be novel, and which will be described in detail herein- Drawmgs With reference to the accompanying drawings s Fig. 1 shows a calling telephone A leadingin to a line switch B. It also shows the set relay C for changing the so-termed normal conductors from the line leadin to the line switch B to the corresponding liank terminals accessible from line finder switch F in Fig. 3. The indicated connector D normally has access to the line leading to telephone A.

Fig. 2 shows a first selector E of a group accessible from the line switch B. It also switch F has a line relay indicates a callin telephone A leading to a line switch L, t e latter havin access to first selector B, second selector third se- "lector D and connector D in Fig. 1," in sequence, to complete a call from the telephone A in Fig. 2 to the tele hone A in Fig. 1.

Fig. 3 shows a'line nder switch F of the present invention involving auxiliary apparatus, the said line finder switch having access'to terminals of a plurality of lines which maybe called through connector D in Fi 1, or random connectors in the exchange 0%- fice containing connector D wherein contact springs of a set relay similar to C are interposed. Each said line accessible from line as shown on'the left aligned with the switch relays.

Fig.4 shows a first selector G companion to and individual to the line finder'switch F in Fig. 3. The first selector F has access to other switches in common with first selector E in Fig. 2. The first level of selectors E and F have common access to the secondary line switch SL. The second level of selectors E and F have common access to second selector B, third selector C and connector D- in sequence, the latter having'access to the line leading to telephone'A. The third level of selectorsE and F have common accessto second selector B, third selector F and conncctor G in sequence, the latter having access to the line leading to tele hone A.

Fig. 5 shows a'secon through the secondary line switch SL. It also shows a third selector I reached from the second selector H.

Fig. 6 shows a connector of the present invention J reached through the third selector I. The connector J has access to operators answering jacks, two of which jacks ,are shown.

Fig. 6A. shows an operators answering plug .and associated operators telephone circuit. The said plug is co-operative with the answering jacks shown in Fi 6.

Fig. 7 shows three order 0 access switches K, L, and M, of a group which switches are (so-operative with the group or groups of connectors of which connector J is one.

selector H reached Fi 12 shows the line finder switch T indivi ual to one of the group of impulse sending mechanism, only one of the latter (Fig. 8) being shown.

Fig. 13 shows one of the wi ers andcooperative bank terminals of t e predetermining switch for governing the number of impulses in the train of impulse series sent.

F1 14 shows the circuit diagram employing t e predetermining switch shown in Fig. 13 to obviate using jumpers in Fi 8. This circuit concerns one of the set re ays (802) in Fig. 8.

Fig. 15 shows a preferred modification of Figs. 1, 9, 10, 11, and 12, for applying an allbnsy tone, and for other objects. 1

Fig. 16 shows a modification of the connection of the attendants jack shown in Fig. 6, introducedwhere indicated by the section line a; V

Fig. 17 shows a preferred modification of Fig. 6 for preventing more than one bar conductor from being unbarred at a time.

Fig. 18 shows the assembly of the figures to display the said first method of employing the present invention.

Fig. 19 shows the assembly of the figures to display the said preferred method'of em- Equipment known rotary class as described on page 53 of Hersheys Automatic Telephone Practice, third edition. However, the line switch B has an added upper wiper forobjects of the present invention.

vThe connector D in Fig. 1 is of the well known type as shown in Fig. 73 of the fourth edition of the said book.

The first selector E in Fig. 2 is of the well known type sometimes called a Powell selector, and described on pages 59 to 61 of the said third edition of Hersheys book. However, a set of eleventh vertical position olfnormal springs and connected circuits belong to the present invention.

The first selector G in Fig. 4 is of the well known said Powell type.

The selectors B C and D in Fig. 2; 13*, o, F and d in Fig.4, and H and 1 in Fig. 5, are like selector G in Fig. 4/

The line switch-L in Fig. 2 is like switch B in Fig. 1.

The connectors D and G in Fig. 4 are like connector D in Fig. 1.

The line finder switch F in Fig. 3 is of the class shown and described on pages 55 to 57 of the third edition of Hersheys book. However, modified in accordance with the present invention.

The connector J in Fig. 6 is of the class of connector D in Fig. 1. However, modified in accordance with the present invention. The operators circuit shown in Fig. 6A is well known, or may be any suitable or other well known one.

The switch elements shown in Fig. 7 belong to the class of switch B in Fig. 1, modified in accordance with the present invention.

belon to the class of switch B in Fig. 1, modified in accordance with the present invention.

The finder switch Q in Fig. 9 is generally like switch F in Fig. 3, modified in accordance with the presentinvention.

Fig. 10 shows a finder switch R enerally like the finder switch shown and escribed on pages 55 to 57 of the third edition of Hersheys book. However, modified in accordance with the present invention.

Fig. 11 shows a finder switchS, like B.

Fig. 12 shows a finder switch T, like R.

It will be understood that any other suitable switches may be substituted for the said well known switches mentioned, without departing from the spirit of the present invention. Also, that the switches s ecific to the present invention may be modi ed by those skilled in the art without departing from the spirit of the present invention, as defined by the sub-joined claims.

It will, of course, be understood that in a commercial embodiment of the resent invention a plurality of switches in a group will be employed 1n place of the exemplary single switches used in disclosing the present nvention, so that a pluralit of calls may be co-existent, the switches in t e groups having predetermined order of use with respect to antecedent co-operative switches.

The switch elements N and O in Fig. 8

Detailed opemtiowlm'tiatz'ng a call from telephone A to telephone A Upon removing the receiver from the switch-hook of telephone A, the line switch B will operate in the well known manner to seize the first idle first selector E. The calling party will then operate his calling device in accordance with the five digits 34341 and thus correspondingly set the selectors E, E and F and connector G. The connection may then be released in the well known manner, responsive to the callin party replacing his receiver on the switchook. A call to telephone A, the telephone number of which is 22531, will be effected in'a generally like manner. It will be noted that the telephones A and A are located tributary to the 3 and 2 ofiice districts, respectively, while the telephone A (No. 42211) is tributary to the 4 ofiice district, reached by the connector D and other connectors of its group.

Setting the set relay 0' to the Lane so I leading to telephone A 80 any call is directed to line 1V 0. 423211 the call wit! be forwarded to telephone A which is No. 22531 tributary to a defer-eat central The party at telephone A will remove his receiver as if to initiate a call, wherein the line switch B will select the first idle first selector E. The party will then operate his calling device dial in accordance with the special setting finger-hold in order to effect a series of eleven open impulses. This will cause the first selector E to operate the eleventh-vertical oil-normal spring set 201. Ground will thereupon be applied over conductor 202 to bank terminal 20 of the group 20 to 23, wiper 25 of'the group 25 to 28, armature 29, conductor 530, spring 31 on relay C,

armature 32 to the winding of relay 33, the latter said relay actuating.

A locking circuit can now be traced through armature 35 to conductor 30 to sustain relay 33 actuated so long as ground exists on conductor 30. The armature 36 disconnects the winding of relay 37. Armature 39 (which makes last) closes an energizing circuit for operating the magnet 40' of relay C. The armature 42 willbe locked in its operated position by the dog 43. It will be noted in this connection that when the spring 31 flexes into engagement withits make contact the armature 36 has already attracted to disconnect the winding of relay 37.

At the time relay 33 actuated to energize the magnet 40, armature 45 will have closed a circuit from the tone source T' to the lower line conductor leadingto telephone A to indicate by specific tone to the party holding the receiverat telephone A that the relay C has operated to set the corresponding line leading from telephone A so that calls thereafter directed to said line will be forwarded to telephone A in accordance with the umpers run from the armatures of relay 802 of the group 801 to 303, as will appear presently.

The shaft of first selector E will, responsive to the actuation of its switching relay 205, rcmtore to normal position, removing the stated ground from conductor 30 and thereby unlocking relay 33 consistent with the slowreleasing properties of relays 206 and 207. The tone applied from source T to telephone A will then cease and the party at telephone A may then hang up his receiver, leaving the contact springs on relay operated.

Unsetting the set relay 0 If it is now assumed that the party at telephone A desires to unset the relay C, he having returned to his telephone after an absence, perhaps, he will remove his receiver and operate his calling device dial in the manner as when he caused relay C to be set, whereupon the first selector E will operate the oft-normal springs set 201 to apply a ground over conductor 30 as before. In view of the spring 31 being at this time flexed against its make contact, disengaged from its resting contact, the ground on conductor 30 will be applied through armature 36 to the winding of relay 37, the latter said relay operatively energizing and locking through its armature 4G to grounded conductor 30. The armature 32 disconnects the winding of relay 33. Armature 48 (which makes last) closes an energizing circuit of magnet 49 for operating the dog 43 for unlatehing armature 42 so that said armature 42 will retract. It will be noted, in this connection, that when the spring 31 flexes back to normal position into engagement with its resting contact as drawn, responsive to the unlatching oi the armature 42, the armature 32 has already attracted to disconnect the winding of relay 33.

At the time relay 37 actuated to energize the magnet 49, armature 50 will close a circuit from the tone source T to the lower line conductor leading to telephone A to indicate by specific tone to the party holding the receiver at telephone A that the relay C has deactuated to restore the line leading to telephone A to normal, unset condition.

The shaft of, first selector E will restore to normal position and ground will be thereby removed from conductor 30 in a brief time after the conductor 30 is caused to be grounded, in the manner as when the'relay C was set.

Mal-tag a call from telephone A to the telephone line leading to telephone A wider the condition that the set relay 0 1'3 set The wipers 51 to 53 of connector D will now be assumed as set upon the bank terminals 55 to 57, respectively, corresponding to line telephone number 42211 leading to telephone A, responsive to the party at telephone A operating the calling dial in accordance with telephonenumber 42211.

When the connector D seizes, ground potential is applied therefrom through its wiper 51, bank terminal 55, conductor 59, spring 60, conductor 61, armature 301, lower winding of relay 302 to the winding of common relay 303. Relay 303 will actuate and operatively energize common relay 304. Armature 305 on relay 302 will be attracted from its resting contact into engagement with its make contact. The armature 301 on relay 302 remains inert at this time.

In this connection, it will be understood that for each line equipped with a set relay like C there will be a specific line relay individual thereto corresponding to relay 302. Also, there will be a set of bank terminals accessible from the finder switch wipers 310 to 313 corresponding to each said line relay. So that when relay 304 actuates the private bank terminal corresponding to 307 for relays corresponding to 302 of all idle said line relays will constitute ground potential. Under the present assumed condition the armae ture 305 on relay 302 is attracted from its resting contact, so that its private bank terminal 307 (and multiples) will be free of ground potential. That is to say, when relay 304 actuates all private bank terminals accessible from switch F of idle lines (and busy lines due to the busy condition) excepting only the private bank terminal of the line having its line relay in calling condition will be guarded against seizure. Thus, when the line relay 302 attracted its armature 305 from its resting contact to its make contact, the line 42211 seized by connector D is the only line unbarred, subject to seizure by the switch F or a switch of its group.

At the time relay 304 actuated it applied. ground potential over common conductor 314,

. armature 315 to the winding of slow-releasing relay 316, the latter said relay actuating. Ground received from guarded private bank terminals is applied through wiper 310. armatures 318 and 319, interrupter armature 320 to the interrupter magnet 321, the latter said magnet driving the wipers 310 to 313 until the wiper 310 fails to receive ground. This will be when it reaches bank terminal 307 of the line being called through connector D. The ground applied through armatures 318 and 319 to the upper terminal of the winding of switching relay 325 while wiper 310 was moving over grounded bank terminals will thus be removed so that the relay 325 will operatively energize from ground applied through armature 322 in series with the interrupter magnet 321, also termed motor magnet.

Relay 316 in switch F being slow-releasing, it remains actuated for an appreciable time after the relay'325 actuates. That is, ground applied through armature 322 will be applied through armature 318, wiper 310, bank terminal 307, armature 305, upper winding of relay 302 to grounded battery to fully operate the relay 302 wherein the armature 301 thereof will attract from its resting contact to its make contact. Remembering that the conductor 61 receives ground from the connector D, it'will be clear that this ground is applied through wiper 310 to sustain relay 325 before the armature 322 has had time to retract. This ground received over conductor 61 also energizes the upper winding of relay 302 to sustain the latter said relay fully actuated. When relay 316 deactuates the conductor 314 will be thus continued through armature 326 to conductor 327 and to armature corresponding to 315 of the next switch of the group (not shown), so that the said next switch will operate if a new call is initiated before the switch F is returned to idleness.

At this time ground applied through wiper 310 is further applied through attracted an mature 329, conductor 330, armature 331 to the Winding of relay 332, the latter said relay actuating. Ground is now applied through armature 335, wiper 313, bank terminal 336, conductor 337 to the winding of relay 802. It will be noted in this connection that the relay 802 is individual to the line 42211 seized by connector D, there being as many relays corresponding to 802 as there are lines served by the finder switch F'.

Also, ground is now applied through armature 340, conductor 341, wiper 808 (of group 805 to 808), bank terminal 809, conductor 810, bank terminal 812, wipers 816 and 815 (of group 815 to 818) bank terminal 819, conductor 820, armature 343, conductor 345 to the winding of relay 823, the latter said relay actuating, a locking circuit being closed through its armature 824, conductor 825, armature 346 to ground. However, the latter said locking circuit is to no operative purpose until the traced primary energizing circuit is opened by the wipers 815 and 816 moving oil the bank terminals they are shown resting upon, as will appear presently.

At the time relay 332 actuated it closed an energizing circuit from the upper winding of relay 401, armature 402, conductor 403, armature 347, conductor 828, armatures 829 and 830 in multiple, conductor 831, armature 348, conductor 349, armature 404 to the lower winding of relay 401, the latter said relay actuating, followed by dependent slow-releasing relay 405.

The ground interrupter I revolves continuously at the rate of approximately twelve revolutions per second, so that the first ground application to conductor 832 following the actuation of relay 823 will be applied through armatures 833 and 834 to the winding of impulse sending relay 835, the latter said relay thus attracting its armature 830 from its resting contact in accordance with the operation of the interrupter I". The armature 838 is in multiple with armature 834, so that the ground applications effective to relay 835 will be coincidently effective to the motor magnet 839 to cause the wipers 815 to 818 to be successively advanced in unison with the operation of relay 835.

When the Wiper 817 engages bank terminal 840 ground is applied from said terminal, armature 841 to the winding of relay 842, the latter said relay actuating to remove the short circuit through the armature 829 so that the armature 830 will send open impulses effective to the line relay 401 in first selector G.

At this time it will be noted that the terminals X on the relay 802, counting from left to right, correspond to the numerically progressive ranks of series of a train of five series of open impulses constituting the digits of the number of the telephone line 22531, wherein the terminals Y directly below the relay 802 determine the number of open impulses in the individual series of the train in correspondence with the jumpers joining the X terminals with a respective Y terminals. The sets of terminals Y refer to di it series from 1 to 0, counting from the eft, and therefore refer to the terminals swept by wiper 815, counting from the right starting with bank terminal 845.

A circuit can now be traced from ground, armature 340, conductor 341, wiper 808, bank terminal 809, armature 846, jumper 847 to the terminal Y corresponding to bank terminal 848 which determines digit 2.

As the wipers 815 to 818 progress, responsive to impulses from the interrupter I, wherein the relay 842 energized at the time wiper 817 reaches bank terminal 840, it willbe clear that, for each successive bank terminal position following 840 reached in the advancement of the wipers, one open impulse will be transmitted by the armature 830 of relay 835 to the line relay 401. However, since bank terminal 848 constitutes ground potential, when the motor magnet deenergizes the second time after the wiper 817 is set upon the bank terminal 840, the wiper 815 will receive ground from bank terminal 848 and apply it through wiper 816, conductor 850 to the winding of slow-releasing relay 851, the latter said relay actuating and locking through its armature 841, wiper 817 to ground on the engaged bank terminal. Re-

ys 835 and 842 are deenergized and maintamed so. This locking ground is also applied through armature 852 to the resting contact of the interrupter armature 853, so that while the relay 851 is locked, ground is applied to cause the interrupter magnet 839 to operate to restore the wipers 815 and 817 to the drawn position, at which time the said locking ground received through wiper 817 

